The invention relates, in general, to hydromechanical and hydraulic mining or cutting and, more particularly, to a tool for hydromechanical and hydraulic mining or for cutting mineral or bituminous materials.
It is well known that the cutting capability of a high speed liquid jet, directed perpendicularly onto the surface of a solid body and moved in translational motion along this surface, can almost be doubled by superimposing an oscillation in the same direction of the continuous translational advance motion, In this way, every individual point in the path is swept several times at a higher rate from different directions. The optimum sweeping speed, depending on a number of parameters, is on the order of magnitude of ten meters per second.
To utilize this improved cutting performance, based on the so-called air hammer effect, the cutting nozzle is reciprocated in translational motion perpendicularly to its longitudinal axis, in the advance direction, or caused to oscillate about an axis which is normal to the advance direction.
The unhindered oscillation of the nozzle is assured only if the nozzle is accommodated in a proper protective housing. Otherwise, it may be blocked or damaged by the material broken up during the cutting operation.
Enclosing the mounting of the nozzle, its swiveling mechanism and drive, however, does not ensure reliable operation so long as water having fine material can penetrate into the aperture through which the jet is discharged.
A known tool of the above-mentioned kind houses an oscillatory nozzle that is driven by a motor through a coupling bar. The elements of the swivel drive of the nozzle partly execute both a rotary and a translational motion. The rotary parts may be only partly axially symmetrical. Even though the housing has small jet discharge apertures, the water with fine material penetrates into the housing. Deposits of such fine material between the fixed and the moving parts of the swivel drive necessarily cause troubles in the operation of the drive. Since mud and water continually penetrate to the swivel drive, an expensive mounting and sealing must be provided for the individual joints.